GB2203265A

GB2203265A - Fuel injection control system

Info

Publication number: GB2203265A
Application number: GB08807591A
Authority: GB
Inventors: Tsunee Iizuka
Original assignee: Fuji Jukogyo KK; Fuji Heavy Industries Ltd
Current assignee: Subaru Corp
Priority date: 1987-04-02
Filing date: 1988-03-30
Publication date: 1988-10-12
Also published as: DE3810692C2; JPS63246429A; DE3810692A1; GB8807591D0; US4819605A

Description

1 3 1 220320PS Fuel Injection Control System for an Automotive Engine The

present invention relates to a fuel injection system for controlling air-fuel ratio of mixture supplied to an engine of a vehicle, and more particularly to a control system for injecting an interrupt fuel during an ordinary fuel injection at acceleration while an air-conditioner is used.

in a known fuel injection system for a motor vehicle, a basic injection pulse width T p is calculated in dependence on an air flow Q, and engine speed N (Tp = K x OIN, where K is a constant). An actually injected injection pulse width T i is determined by correcting the basic injection pulse width T p in accordance with engine operating conditions such as idling and is wide open throttle., In order to compensate for response delay of an air-flow meter for detecting the air flow Q at the acceleration of the vehicle, Japanese Patent Laid Open 60-17247 discloses a control system wherein an auxiliary fuel is.injected when a differential of pressure in an intake pipe is larger than a predetermined value, which indicates the acceleration of the engine. An auxiliary fuel injection pulse width TACC for acceleration is obtained in dependence on a predetermined correction coefficient KACCL for acceleration and correction constant T CONST (T ACC = KACCL x T p + T CONST).

However, correction coefficient K ACCL and constant T CONST are set to have a proper air-fuel ratio under operating conditions without loads such as an air-conditioner.

Accordingly, the power of the engine decreases when the air-conditioner is used. In order to maintain the same power, the driver of the vehicle depresses an accelerator pedal so that the opening degree of the throttle valve is increased to induct more air to increase the engine speed. The increase of the air flow Q causes.an increases of the basic fuel injection pulse width T P However, since the coefficient K ACCL and the cons,.'-ant T are set irrespective of the operation of the CONST aiT-conditioner, auxiliary fuel injection pulse width T ACC also increases with increase of the engine speed. Thus, air-fuel mixture becomes excessively rich to reduce the combustion efficiency, thereby causing hesitation or stumble at the start and acceleration oil the vehicle and hence decreasing the d_riveability.

The pi.esent invention secks to provide fuel injection control system for controlling auxiliary fuel injection at acceleration while using the air-conditioner, to prevent the reduction of the combustion efficiency., thereby improving the drJveabilitY at starting and acceleration of the vehicle.

According to the present invention, there is provided 2 X.

a fuel injection system for an automotive engine having an airconditioner, for producing a fuel injection pulse width signal for a fuel injectort the system comprising: means for detecting acceleration of the engine and for producing an acceleration signal; an air-conditioner switch for producing an air-conditioner signal when the air conditioner switch is closed; auxiliary injection means responsive to the acceleration signal and the air-conditioner signal when the switch is closed for producing a first auxiliary injection pulse width signal which is used to control fuel injection independent of the main fuel injection, which first signal has a smaller value than a second auxiliary injection pulse width signal which is produced when the air-conditioner switch is opened, thereby reducing auxiliary injection pulse width.

Preferably, the system has a neutral switch for producing a neutral signal when a transmission of a vehicle is in a neutral state, the auxiliary injection means being arranged to further respond to the neutral signal for producing an auxiliary injection pulse width third signal having a larger value than the second signal, thereby increasing the auxiliary injection pulse width. The auxiliary injection means has coefficients for correcting the auxiliary injection pulse width signal, and the coefficients decrease in value with increase of temperature of a coolant of the engine.

f 1 J A preferred embodiment of the invention will now be describear by way of example, with reference to the accompanying drawings, wherein:

Fig. 1 is a schematic illustration showing a system for controlling the operation of an internal combustion engine for a motor vehicle; rigs. 2a and 2b show a block diagram of a control unit used in a system of the embodiment; rig. 3 is a graph showing a relationship between acceleration correction coe'L.'Licienlf.-. and coolant temperature; Fig. 4 is a graph showing a relationship between constant and coolant temperature; and Fig. 5 is a flowchart showing the operation of the system of the present embodiment.

Referring to Fig. 1, an internal combustion enaine 1 for a motor vehicle is supplied with air through an air cleaner 2, intake pipe 3 and a throttle valve 4, mixing with fuel injected from an injector 5. Exhaust gas of the engine 1 is discharged through an exhaust pipe 6 and a catalytic converter wire is provided A mass air-flow meter 8 employing a hot on the intake pipe 3 and an 0 2- sensor 11 is mounted in the exhaust pipe 6. output signals of the meter 8 and sensor 11 are applied to a control unit 10. The control unit 10 is also supplied with output signals of a crank angle sensor 9, 1 -5 1 1 1 throttle position sensor 12, coolant temperature sensor 13, neutral switch 14 for detecting the neutral state of a transmission (not shown), and air-conditioner switch 15. The control unit 10 produces an actuating signal to operate the injector 5.

Referring to Figs. 2a and 2b, the control unit 10 comprises an engine speed calculator 20 which calculates engine speed dependent on a signal from the crank angle sensor 9, and a basic injection pulse width calculator 21 to which an engine speed signal N from the engine speed calculator 20 and air flow si-gnalQ from the mass air-flow mezer 8 are applied. The basic injection pulse width T p is obtained by the following equation.

TP R x Q/N (K is constanf.. The output signal T p is applied to an injection pulse width calculator 22 to obtain an injection pulse width T i by correcting the basic injection pulse width T p in accordance with a signal from 0 L.

-sensor 11, coolant temperature signal T 2 W from the coolant temperature sensor 13 and th-rottle position signal e of the throttle position sensor 12. The injection pulse width T i is calculated by the 'Lollowing equation.

T i = T p X COEF X >', where COEF is a miscellaneous coelf-ficient comprising various correction or compensation coefficients obtained &from memories dependent on coolant temperature, and throttle position, and Xl, -6 1 is a correcting coefficient dependent on the feedback signal of the 0 2_ sensor 11.

The control unit 10 further comprises an acceleration deciding section 23 which determines that the vehicle is accelerated when the throttle position signal e. representing the throttle opening degree changes at higher speed than a predetermined value. Output signals of the acceleration deciding section 23, neu tral switch 14, air-conditioner switch and coolant temperature signal T W are applied to an acceleration correction coefficient and constant providing section 24 having an acceleration correction coefficient memory 25 and a constant memory 26. The acceleration correction coefficient memory 25 comprises three lockup tables storing acceleration correction coefficients K ACCLl' K ACCL2 is and K ACCL3' respectively. The constant memory 26 comprises three lookup tables storing constants T CONST1' 'CONST2 and T CONST3' respectively. The coe-f-'icienlb-. table and the constan.116 table are selected dependent on whether the neutral switch 14 and the air-conditioner switch 15 are closed or opened. The selection of the coefficient table and constant table are as follows.

14 i 1 1 AIR-CONDITIONER SWITCH NEUTRAL SWITCH CLOSED OPENED K ACCLI K ACCL1 CLOSED T fr CONSTI J.

CONSTI K ACCL2 K ACCL3 OPENED fr 1r CONST2 -CONST3 Relationships among the coefficients K and ACCLI ACCL3 among the constants T CONSTI to T CONST3 are as follows.

K ACCL1 > "ACCL3 > "ACCL2 T CONSTI-> T CONST3 > T CONST2 An acceleration correction coefficient K ACCL and constant T are respectively read out from the selected table in CONST dependence on the coolant temperature. As shown in Figs. 3 and the constant T and 4, both the coefficient XACCL CONST decrease with the rise of the coolant temperature.

The derived correction coefficient "ACCL and constant TCONIST are fed to an auxiliary injection pulse width calculator 27 to which basic injection pulse width T p and the acceleration signal from the acceleration deciding section 23 i 1 is are supplied. The equation for obtaining auxiliary injection pulse width TACC is as follow s.

TACC = KACCL x TP ' TCONST Injection pulse widths T. and T ACC are independently fed to the injector 5, respectively.

The operation of the present embodiment is described hereafter with reference to the flowchart shown in Fig. 5.

Att a step SI, it is determined that the engine is accelerated when the changing rate of the opening degree of the throttle valve for a predetermined period, for example 40 msec., is larger than a predetermined value. If the acceleration is determined, the program proceeds to a step S2 where it is determined whether the air-conditioner switch is on or off. When the air conditioner switch is off, it is further determined at a step S3 whether the neutral switch is on. When the neutral switch is off, which means.1--hall- the vehicle is being accelerated, an acceleration correction coefficienb. KACCL3 and a constant TCONST3 are derived and set at a step S4.

On the other hand, when it is determined at the step 53 that the neutral switch is on, which means that'accelerator pedal is depressed during idling (racing), correction coefficient XACCL1 and constant TCONST1 are set at a step 5.

When it is determined that the air-conditioner switch is on at the step S2, the program proceeds to a step S6 where it is also determined whether the neutral switch is on. When the 1 14 is neutral switch is on, the program goes to the step SS. When it is determined that the neutral switch is off at step S6, acceleration correction coefficient KACCL2 and constant TCONST2 are set at a step 57. At each step, the acceleration correcting coefficient and the constant are read-out in dependence on the coolant temperature signal T W.

Since the values of the coefficient KACCL2- and the constant T CONST2 are the smallest, the auxiliary injection pulse width T ACC becomes small. Accordingly, at acceleration of the vehicle while the air-conditioner is used, that is when the neutral switch is off and the air-conditioner switch is closed, the air-fuel mixture is prevented from becoming excessively rich.

In addition, when the coolant temperature is low, the values of the coefficient and constant are large so tha-A the auxiliary pulse width is increased.

In accordance with the present invention, the correclb-.ion coefficient and constant at the acceleration of the vehicle is decreased while Che air-conditioner is used. Therefore, the fuel quantity for a predetermined time is determined to a value same as that of a state while the aircondltioner is not used, in spite of the increase in basic. fuel injection pulse width. Thus, the air-fuel mixture is prevented from becoming over-rich.

While the presently preferred embodiment of the present invention has been shown and described, it is to be understood V - 4 j that.this disclosure is for the purpose of illustration and that various changes and Modifications may be made without departing from the spirit and scope of the invention as set forth in the appended claims.

k f A

Claims

Claims:

1. A fuel injection system for an automotive engine having an airconditioner, for producing a fuel injection pulse width signal for a fuel injector. the system comprising: means for detecting acceleration of the engine and for producing an acceleration signal; an air-conditioner switch for-producing an air-conditioner signal when the air conditioner switch is closed; auxiliary injection means responsive to the acceleration signal and the airconditioner signal when the switch is closed for producing a first auxiliary injection pulse width signal which is used to control fuel injection independent of the main fuel injection, which first signal has a smaller value than a second auxiliary injection pulse width signal which is produced when the air- conditioner switch is opened, thereby reducing auxiliary injection pulse width.

2. A system as claimed in claim 1, having a neutral switch for producing a neutral signal when a transmission of a vehicle is in a neutral state, the auxiliary injection means being arranged to respond to the neutral signal for producing a third auxiliary injection pulse width signal having a larger value than the second signal, thereby increasing the auxiliary injection pulse width.

Z

3. A system as claimed in claim 1, wherein the auxiliary injection means stores coefficients for correcting the auxiliary injection pulse width signal.

4. A system as claimed in claim 3, wherein the coefficients decrease in value with increase of temperature of a coolant of the engine.

5. A fuel injecti6n control system for an automotive engine having an air-conditioner and a fuel injection system which produces an injection pulse width signal for main fuel injection, the system comprising: detector means for detecting acceleration of the engine and for producing an acceleration signal; an air-conditioner switch for producing an air-conditioner signal when the air-conditioner switch is closed; auxiliary injection means responsive to the acceleration signal and airconditioner signal for producing an auxiliary injection pulse width first signal which is injected independent of the main fuel injection; the auxiliary injection pulse width first signal having a smaller value than a second signal when the air-conditioner switch is opened, thereby reducing auxiliary injection pulse width.

A k 0

6. The system according to claim 5. further comprising a neutral switch for producing a neutral signal when a transmission of a vehicle is in a neutral state, the auxiliary injection means being arranged to further respond to the neutral signal for producing an auxiliary injection pulse width third signal having a larger value than the second signal, thereby increasing the auxiliary injection pulse width.

7. The system according to claim 5, wherein the auxiliary injection means has coefficients for correcting the auxiliary injection pulse width signal.

8. The system according to claim 7, wherein the coefficients decrease in value with increase of temperature of a coolant of the engine.

9. A fuel injection system substantially as herein described, and with reference to the accompanying drawings.

Publ1Bhed 1988 at The Patent Office, State House, 68171 High Holborm London WC1R 4TP. Further copies may be obtained from The Patent Office, Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Multiplex techniques ltd, St Mary Cray, Kent. Con- 1187.